Wire-like Bundle Arrays of Copper Hydroxide Prepared by the Electrochemical Anodization of Cu Foil

Nanostructured copper compounds were grown by electrochemical anodization of copper foil in aqueous NaOH under varying conditions including electrolyte concentration, reaction temperature, current density, and reaction time. Their morphology and atomic composition were investigated by using SEM, TEM, XRD, EDS and XPS. At the conditions ([NaOH] = 1 M, 20 °C, 2 mA cm -2 ), wire-like orthorhombic Cu(OH) 2 nanobundles with an average width of 100 - 300 nm and length of 10 μm were synthesized with the preferential [100] growth direction. Furthermore, when the concentration decreased to 0.5 M NaOH, the 1D nanobundle structure became narrower and longer without any change in compositions or crystalline structure. Side reaction pathways appeared to compete with the 1D nanostructure formation channels: the formation of CuO nanoleaves at 50 °C via the sequential dehydration ofCu(OH) 2 , CuO/Cu 2 O aggregates in 4 M NaOH, and Cu 2 O nanoparticles and CuO nanosheets at lower current density.